OBJECTIVETo evaluate biomechanical properties in different methods of internal fixation combined with distal tibiofibular syndesmosis injury, in order to provide a theoretical basis for clinical choice.

METHODSSix lower limbs specimens were collected and divided into 5 groups, including normal group, distal tibiofibular syndesmosis injury (injury group), 3 cortexes group, 4 cortexes group and hook-plate fixation group. Neutral position, plantar flexion position (30°), dorsiflexion (20°) supination external rotation position of foot movement were simulated on universal materials tester. Strength, stiffness and stability of ankle joint in 4 kinds of motion conditions were measured.

RESULTSThere was significant differences in strength and stiffness of ankle joint between injury group and normal group in 4 different kinds of motion conditions (P<0.05). Strength and stiffness of ankle joint in 3 cortexes group, 4 cortexes group and hook-plate fixation group were improved obviously in 4 different kinds of motion conditions, and biomechanical indexes were recovered normally or better than normal group. Stiffness of the three fixation groups were better than normal group,but there was no significant differences among three groups (P > 0.05), while stiffness of hook-plate fixation group was closed to normal group.

CONCLUSIONFor distal tibiofibular syndesmosis injury, 1 screw with 3 cortexes, 4 cortexes and hook-plate had a positive impact on strength, stiffness and stability of distal tibiofibular syndesmosis injury stress,and could restore the normal stabllity of ankle joint after reconstruction. While fixing by screw fixation would limit the rototary motion of ankle joint,ankle mortise could not adapt to changes of talus bone, thus induces screw breakage and traumatic arthritis. Hook-plate fixation is more suitable than 3 cortexes or 4 cortexes fixation for bilmechanical properties,and its' stress is more balance and can reduce postoperative complcations.